In a gas turbine, a diffuser is installed, which is connected to an axial flow rotating machine, such as a compressor or a turbine, on the downstream side of the axial flow rotating machine. Deceleration and pressure (static pressure) recovery of working fluid, such as compressed air or combustion gas, is performed by the diffuser (refer to Japanese Unexamined Patent Application Publication No. 2005-290985A and Japanese Unexamined Patent Application Publication No. H08-210152A, for example).
In a gas turbine 102 illustrated in FIG. 12, a diffuser 101, which is connected to a turbine on the downstream side of the turbine, is formed by concentrically arranging an inner-circumferential inner wall 108 with an outer-circumferential inner wall 109 that is formed with the diameter thereof increasing in the direction of the downstream side. A circular flow path 110 is formed between the inner-circumferential inner wall 108 and the outer-circumferential inner wall 109. A gas turbine 2 is provided with a turbine casing 3 on the outer side thereof. Sets of a stator blade 5 and a rotor blade 6 are arranged in a plurality of stages inside the turbine casing 3.
A rear end of a rotor 20, to which a final-stage rotor blade 6f is attached, is supported by a bearing 12. A bearing housing 11 that houses the bearing 12 is concentrically supported with the center of the turbine casing 3 by a plurality of struts 14 that are radially arranged so as to traverse the flow of the working fluid. The struts 14 are covered by a strut cover 15 so as to inhibit the struts 14 from being exposed to high-temperature exhaust gas. Furthermore, downstream of the struts 14, a cylindrical manhole 16 is provided which are radially arranged so as to traverse the flow of working fluid.
Next, a diffuser that is connected to a compressor on the downstream side of the compressor will be described with reference to FIG. 13. A turbine 102B includes a compressor 50, a combustor 51 to which compressed air generated in the compressor 50 is supplied, and a turbine 52. The compressor 50 has a structure in which sets of a stator blade 5B and a rotor blade 6B are arranged in a plurality of stages.
A diffuser 101B, which is connected to the compressor 50 on the downstream side of the compressor 50, is formed by concentrically arranging an inner-circumferential inner wall 108B, which has the diameter thereof decreasing in the direction of the downstream side from a position downstream of a final blade 7, with an outer-circumferential inner wall 109B, which has the diameter thereof increased in the direction of the downstream side from the position.
The final blade 7 is a blade that is located furthest downstream among the plurality of stator blades 5B and the plurality of rotor blades 6B. When an OGV, namely, an outlet guide blade is located downstream of the stator blades 5B and the rotor blades 6B, the OGV becomes the final blade 7. A circular flow path 110B is formed between the inner-circumferential inner wall 108B and the outer-circumferential inner wall 109B.